Radiation refrigeration self-cleaning coated fabric and preparation method thereof

Abstract

The invention discloses a radiation refrigeration self-cleaning coated fabric and a preparation method thereof, and belongs to the technical field of industrial textiles, TPU and PVDF are used as matrixes, nanoscale hydrophobic SiO2 particles are added, SiO2 (at) TPU / PVDF coating finishing liquid is prepared, the coated fabric realizes an enhanced synergistic refrigeration effect through a radiation refrigeration mechanism and composite application of the coated fabric and a fabric, and the radiation refrigeration self-cleaning coated fabric has the advantages that the radiation refrigeration self-cleaning coated fabric has a good radiation refrigeration effect. The coating finishing liquid is uniformly loaded on the surface of a fabric by using a scraper type film coating machine to form a coated fabric which shows excellent radiation refrigeration capacity, the binding strength between the coating and a fabric substrate is remarkably enhanced by using TPU, the stability and durability of the coating in long-term use are ensured, and the fabric is endowed with a super-hydrophobic self-cleaning function by using a coating microstructure. The adhesion of dirt and dust is effectively prevented, the cleaning frequency is reduced, and the durability of the coating is further improved, so that the coating is particularly suitable for producing high-performance fabrics, especially outdoor thermal management and sunscreen clothes.

Description

Technical Field

[0001] The invention belongs to the technical field of industrial textiles, and particularly relates to a radiation cooling self-cleaning coated fabric and a preparation method thereof. Background Art

[0002] As the global economy continues to develop, energy consumption is rising year by year, carbon emissions are exceeding standards and air pollution is intensifying, and extreme heat waves are occurring frequently, leading to a surge in global demand for cooling energy. Passive radiative cooling technology, as a zero-energy solution, reflects sunlight (0.25-2.5μm) and uses the "atmospheric transparent window" (8-13μm) to radiate heat into outer space. It has shown great potential in energy-saving buildings, photovoltaic cooling, and personal thermal management. However, existing radiative cooling materials still have significant defects in dynamic adaptability, environmental durability, and multifunctionality.

[0003] In the prior art, radiative cooling materials generally adopt static optical design. For example, patent CN 114736566A proposes a smart window film based on vanadium dioxide (VO2), which achieves thermo-variable temperature through a HfO2 / VO2 / HfO2 sandwich structure. However, such materials have the following problems: (1) They rely on the phase change characteristics of VO2 and can only achieve a limited temperature response range (such as cooling in summer and partial reflection adjustment in winter), and cannot completely avoid the increase in heating energy consumption caused by excessive cooling in winter; (2) They are mainly targeted at transparent substrates (such as glass), have complex structures and high packaging requirements, and are difficult to adapt to large-scale applications on non-transparent substrates (such as textiles); (3) They do not integrate self-cleaning functions and are easily eroded by rain and contaminated by dust when used outdoors for a long time, resulting in optical performance degradation.

[0004] Other related technologies, such as patent CN 212583532 U, propose a smart window device using hydroxypropyl cellulose hydrogel. While this device modulates solar transmittance through thermochromism, its liquid injection layer suffers from poor packaging stability and durability, and is also limited to transparent substrates. Patent CN 109989002A optimizes solar regulation efficiency through a multilayer thin film structure, but fails to address the material's surface hydrophobicity and self-cleaning capabilities. In practical applications, surface contamination can easily reduce radiative cooling efficiency.

[0005] More importantly, existing radiative cooling materials (including the above-mentioned patents) mostly focus on building or equipment cooling scenarios, while ignoring the key needs for wearable textiles: on the one hand, the moisture permeability, breathability, flexibility and wearing comfort of textiles need to be synergistically optimized with radiative cooling performance; on the other hand, color diversity (such as dark clothing) often leads to a decrease in reflectivity in the ultraviolet-visible light band, weakening the cooling effect. At the same time, existing coating processes (such as sol-gel method, magnetron sputtering) are difficult to construct a multifunctional structure with high reflectivity, high infrared emissivity and super-hydrophobicity on the surface of flexible fibers, resulting in the material facing bottlenecks such as poor durability, easy pollution and single function in actual use. The purpose of the present invention is to provide a new method for preparing a radiative cooling self-cleaning coated fabric, which aims to overcome the shortcomings of existing materials through reasonable material combination and preparation process, achieve high performance and multifunctionality of the coating, and promote the development of energy-saving and environmentally friendly materials. Summary of the Invention

[0006] Technical issues solved:

[0007] This application addresses the shortcomings of the existing technology and solves technical problems such as poor coating thickness, durability, self-cleaning performance and radiative cooling efficiency. In response to the challenges faced by fabrics on the market in terms of cooling function and comfort, it provides a radiative cooling self-cleaning coating fabric and its preparation method. By optimizing the selection of materials and the preparation process, a copolymer of polyvinylidene fluoride (PVDF) and thermoplastic polyurethane (TPU) is used, and hydrophobic nano-silica SiO2 is uniformly doped, which significantly improves the scattering and microporous structure of the coating, thereby maximizing the reflectivity of sunlight in the visible light wavelength range. In addition, the design of controlling the color change of the coating not only helps to improve the material's reflectivity within the sunlight range, but also enhances the cooling effect, while improving the material's aesthetics and market adaptability. The introduction of silica further enhances the emission capacity of mid-infrared radiation and improves the radiative cooling efficiency. These innovative designs effectively respond to the growing demand for cooling, provide a new, efficient and environmentally friendly approach for the field of personal thermal management, and promote sustainable development of material science and technology progress.

[0008] Technical solution:

[0009] To achieve the above objectives, this application is implemented through the following technical solutions:

[0010] A method for preparing a radiant cooling self-cleaning coating fabric, using polyvinylidene fluoride (PVDF) and thermoplastic polyurethane (TPU) as a matrix to prepare a PVDF / TPU copolymer, doping the PVDF / TPU copolymer with nano-silicon dioxide (SiO2) particles to ensure that the nano-SiO2 particles are evenly distributed in the PVDF / TPU copolymer to obtain a SiO2@PVDF / TPU coating finishing solution, and

[0011] The SiO2@PVDF / TPU coating finishing liquid and the fabric are compounded by a blade coating machine to form a stable SiO2@PVDF / TPU coated fabric, namely, a radiant cooling self-cleaning coated fabric.

[0012] Furthermore, the coating finishing liquid is prepared by dissolving PVDF in a DMF solution, stirring and mixing at 50°C to 60°C for 1h to 2h to obtain a precursor solution, dissolving TPU in the precursor solution, stirring and mixing at 20°C to 30°C for 0.5h to 1h, adding nano-SiO2 particles, and degassing at 60-100W ultrasound for 30-60min to obtain a coating finishing liquid, wherein the nano-SiO2 particles are hydrophobic silica.

[0013] Furthermore, the mass ratio of PVDF to TPU in the PVDF / TPU copolymer is 9-11:10.

[0014] Furthermore, the mass ratio of nano-SiO2 particles:PVDF / TPU copolymer is 14-15:50.

[0015] Furthermore, the fabric is cotton fabric, polyester fabric, nylon fabric or blended fabric.

[0016] Furthermore, the fabric is polyester Oxford cloth.

[0017] Furthermore, the scraper speed in the scraper coating machine is 20 mm / s, and the scraping length is set to 200 mm.

[0018] Furthermore, the thickness of the SiO2@TPU / PVDF coating is 500 μm.

[0019] Furthermore, the specific preparation method of the SiO2@PVDF / TPU coated fabric is as follows:

[0020] S1. Add polyvinylidene fluoride (PVDF) pellets to a DMF solution and magnetically stir at 50°C to 60°C for 1 to 2 hours to obtain a softened PVDF precursor solution.

[0021] S2. Add thermoplastic polyurethane (TPU) pellets to the softened PVDF precursor solution and magnetically stir at 20° C. to 30° C. for 0.5 h to 1 h to obtain a PVDF / TPU copolymer precursor solution.

[0022] S3, adding nano-SiO2 particles to the PVDF / TPU copolymer precursor solution, and performing ultrasonic treatment with an ultrasonic disperser at a power of 60 to 100 W for 30 to 60 minutes to achieve fine crushing of the nano-SiO2 particles and degassing of the solution to obtain a coating finishing solution;

[0023] S4. The coating finishing liquid is evenly coated on the surface of the fabric by a doctor blade coating machine to obtain a radiant cooling self-cleaning coating fabric.

[0024] The present application also discloses a radiative cooling self-cleaning coated fabric prepared by any of the above preparation methods.

[0025] Principle explanation: This technical solution combines the excellent properties of PVDF and TPU to form a composite coating with self-cleaning and radiant cooling functions. PVDF has excellent chemical stability and UV resistance, while TPU provides good mechanical properties and elasticity. This combination makes the coating not only durable, but also can achieve effective thermal management in high temperature environments; the addition of nano-SiO2 further improves the microstructure of the coating, so that a rich microporous structure is formed on its surface, which not only improves the scattering of the coating, but also increases its self-cleaning performance; the microporous structure can effectively capture water molecules, causing water droplets to form beads on the surface, thereby quickly draining away dust and dirt and achieving a self-cleaning effect; combined with the principle of radiant cooling, the coating can effectively reflect solar radiation and dissipate heat, reducing the temperature of the fabric and improving wearing comfort. Under extreme weather conditions, the composite effect of the coating can significantly improve the user's thermal management experience, providing a more environmentally friendly and efficient solution, thereby achieving a technical effect of 1+1>2 and meeting the market's growing demand for high-performance textile materials.

[0026] Beneficial effects:

[0027] This application provides a method for preparing a radiant cooling self-cleaning coated fabric, which has the following beneficial effects compared to the prior art:

[0028] 1. This application uses polyvinylidene fluoride (PVDF) and thermoplastic polyurethane (TPU) as matrices, doped with nano-silica (SiO2) particles with excellent radiative cooling properties. This innovative material combination not only ensures the uniform distribution of the nanoparticles in the coating, thereby effectively reflecting visible and infrared light from sunlight, but also emitting 8-13μm mid-infrared light, significantly reducing the temperature of the fabric surface. Simultaneously, the combination of PVDF and TPU effectively solves the problem of insufficient bonding strength of PVDF alone, enhancing the adhesion and durability of the coating. Furthermore, by optimizing the doping ratio and dispersion method of silica, the defect of single silica being prone to powdering is overcome, thereby improving the overall performance and service life of the coating.

[0029] 2. The coating of this application has excellent super-hydrophobic properties, which can effectively prevent the adhesion of water, oil and dirt, significantly improving the self-cleaning ability of the fabric. The super-hydrophobic coating causes liquid to form water droplets on the fabric surface, which slides off quickly, removing surface dirt. This property not only reduces the need for cleaning, saves water resources and detergent use, but also reduces maintenance costs, extends the service life of the fabric, and provides users with a more convenient user experience.

[0030] 3. The radiant cooling self-cleaning coated fabric of this application offers significant advantages in cooling and self-cleaning properties, making it widely suitable for outdoor activities, sportswear, professional workwear, and everyday wear. Its outstanding performance enables it to meet market demand for high-performance, convenient, and easy-to-maintain clothing fabrics, providing lasting comfort for the wearer, particularly in hot summers and high-temperature work environments.

[0031] 4. The coating material used in this application is economical and the preparation method is relatively simple, which can effectively reduce production costs. The materials used, such as PVDF and TPU, not only have good performance, but are also relatively common and easily available in the market. This makes the commercial application of this coating more attractive and can bring higher economic benefits to manufacturers.

[0032] 5. The coating of this application has good durability and can maintain its excellent performance under various environmental conditions. Although the coating itself is not soft, its strong structure ensures that it can maintain the cooling and self-cleaning effects during long-term use, making it an ideal choice for high-performance clothing, especially for occasions requiring durability and high functionality. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram of the cross-sectional structure of a composite fabric of a radiative cooling nanofiber membrane and ordinary polyester fabric according to Example 2 of the present application;

[0034] Figure 2 Spectral graphs of the spectrum test of Example 1 and Comparative Example 1 of the present application;

[0035] Figure 3 This is a comparison chart of the cooling tests of Example 1 and Comparative Example 1 of the present application.

[0036] Explanation of the accompanying drawings: 1. Radiant cooling self-cleaning coating, 2. White polyester Oxford fabric. DETAILED DESCRIPTION

[0037] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art may make various changes or modifications to the present invention, and equivalent changes or modifications also fall within the scope defined by the claims of the present application.

[0038] Example 1:

[0039] A method for preparing a radiant cooling self-cleaning coated fabric comprises the following steps:

[0040] S1. Polyvinylidene fluoride (PVDF) pellets are added to a DMF solution and magnetically stirred at 50°C to 60°C for 1 to 2 hours to obtain a softened PVDF precursor solution. DMF is used as the solvent, and the solvent evaporates during the preparation process. During this process, friction between the pellets and the solvent, between the pellets, and between the pellets and the instrument wall generates heat. This, combined with external heating from the instrument, causes the PVDF copolymer to quickly enter a softened state and exhibit strong adhesion properties.

[0041] S2. Add thermoplastic polyurethane (TPU) pellets to the softened PVDF precursor solution and magnetically stir at 20° C. to 30° C. for 0.5 h to 1 h to obtain a PVDF / TPU copolymer precursor solution.

[0042] S3, adding nano-SiO2 particles to the PVDF / TPU copolymer precursor solution, and performing ultrasonic treatment for 30 to 60 minutes at a power of 60 to 100 W using an ultrasonic disperser to achieve fine crushing of the nano-SiO2 particles and degassing of the solution to obtain a coating finishing solution. The nano-SiO2 particles are hydrophobic silica. The surface treatment agent can more effectively locally treat the nanoparticles, significantly reducing the surface energy of the particles and avoiding the re-aggregation of the hydrophobic SiO2 nanoparticles. The viscous drag force of the PVDF / TPU copolymer and the high shear force generated by the ultrasound work together to ensure uniform coating between the hydrophobic SiO2 nanoparticles and the PVDF / TPU copolymer pellets.

[0043] S4, the coating finishing liquid is evenly coated on the surface of the fabric by a scraper-type coating machine, and the thickness of the SiO2@PVDF / TPU coating is

[0044] 500μm, a radiative cooling self-cleaning coating fabric was prepared, and the coating formed by PVDF / TPU copolymer and silica was

[0045] The microporous structure, high scattering properties, and the color of the material itself combine to create a white coating. The polyvinylidene fluoride (PVDF) accounts for 7.0% to 7.2% by weight of the coating finishing liquid, the thermoplastic polyurethane (TPU) accounts for 7.0% to 7.2% by weight of the coating finishing liquid, and the hydrophobic silica accounts for 4.2% to 4.4% by weight of the coating finishing liquid.

[0046] The fabric is cotton fabric, polyester fabric, nylon fabric or blended fabric, preferably polyester Oxford cloth.

[0047] The radiant cooling self-cleaning coating finishing liquid and the polyester Oxford fabric are coated with a blade coating machine using a blade coating technique to form a stable coating fabric. The specific steps are as follows:

[0048] Step 1: Fix the polyester Oxford cloth on the PET film and use a hot press at a temperature of 120°C for 20 seconds to make the polyester Oxford cloth flat and ensure that the subsequent coating is evenly prepared.

[0049] Step 2: Fix the PET film containing polyester Oxford cloth on the equipment workbench;

[0050] Step 3: Set the parameters of the scraper coating machine, set the temperature to 20℃-30℃, turn on vacuum adsorption, set the scraper speed to 20mm / s, and set the scraping length to 200mm;

[0051] Step 4: Pour the coating finishing liquid evenly on the scraper, start the scraper coating machine, and drive the coating finishing liquid to move at a constant speed until it is evenly covered on the surface of the polyester Oxford cloth;

[0052] Step 5: The coating solution is naturally cooled to room temperature. A quality inspection is then conducted to ensure the surface is smooth, wrinkle-free, bubble-free, and that the adhesive strength and hydrophobicity meet the standards. This results in the radiant cooling, self-cleaning coated fabric. Clothing made with the radiant cooling, self-cleaning fabric coating provides a cool, comfortable, and self-cleaning effect.

[0053] This application discloses a uniquely designed radiative cooling, self-cleaning fabric coating. The fabric effectively reflects visible and infrared sunlight while simultaneously dissipating heat within the atmospheric window of 8 to 13 μm through infrared radiation, thereby achieving a cooling effect. The coating's matrix is composed of a TPU and PVDF copolymer, uniformly dispersed with SiO2 nanoparticles, forming a SiO2@TPU / PVDF coated fabric. Figure 2 The working principle of this radiative cooling technology was demonstrated, showing that when full-spectrum sunlight strikes the coating's surface, it effectively reflects both visible and infrared light. Simultaneously, the coating emits heat through specific wavelengths, penetrating the atmosphere and achieving excellent radiative cooling. Through unique material selection and structural design, this invention achieves excellent performance in both sunlight reflection and infrared heat emission in the SiO2@TPU / PVDF coated fabric, providing an effective cooling solution.

[0054] Furthermore, the coating's microporous structure imparts superhydrophobic, self-cleaning properties to the fabric. This microstructure significantly reduces the contact angle of water, allowing water droplets to bead up on the surface and quickly roll off, carrying away attached dust and dirt, thereby keeping the coating clean. This self-cleaning property extends the lifespan of the coated fabric and reduces maintenance costs during daily use. Despite these features, the coating maintains a light, soft texture, providing a comfortable experience for the wearer.

[0055] This embodiment of the present invention focuses on the interaction between the Si-O-Si bond vibration absorption peak in SiO2 and the atmospheric window. This property significantly enhances heat emission in the mid-infrared band. The proportion of SiO2 nanoparticles in the radiative cooling coating directly affects its cooling effect. If the content of hydrophobic SiO2 nanoparticles is too high, it may cause particle aggregation during the coating process.

[0056] Therefore, in order to achieve the best radiative cooling performance, the proportion of hydrophobic silica in this embodiment is set between 4.2% and 4.4%. At the same time, in order to ensure the excellent radiative cooling effect and stable solar reflectivity of the SiO2@TPU / PVDF coated fabric,

[0057] The mass percentage of TPU and PVDF is kept between 7.0% and 7.2%. This combination not only ensures the efficient cooling capacity of the coating, but also maintains its overall stability and functionality.

[0058] Example 2:

[0059] A method for preparing a radiant cooling self-cleaning coated fabric comprises: using thermoplastic polyurethane (TPU) as a matrix and DMF as a solvent. The solvent evaporates during the preparation process and is doped with nano-silicon dioxide (SiO2) particles uniformly distributed in the TPU matrix to obtain a coating finishing liquid. The SiO2@TPU coating finishing liquid is compounded with the fabric using a blade-type coating machine to form a stable composite coating fabric, namely, a radiant cooling self-cleaning coated fabric. The coating formed by the TPU and silicon dioxide appears white due to its surface microporous structure and high scattering properties, as well as the color of the material itself.

[0060] The coating finishing liquid is prepared by dissolving TPU in DMF, stirring and mixing at 20-30°C for 0.5-1h, adding nano-SiO2 particles, and degassing at 60-100W ultrasonic for 30-60min. The nano-SiO2 particles are hydrophobic silica.

[0061] The mass percentage of the thermoplastic polyurethane in the coating finishing liquid is 14.3%-14.4%, and the mass percentage of the hydrophobic silicon dioxide in the coating finishing liquid is 4.2%-4.4%.

[0062] The scraper speed of the scraper coating process is 20 mm / s, and the scraping length is set to 200 mm.

[0063] In order to enhance the radiation and ensure that the hydrophobic SiO2 nanoparticles are evenly dispersed in the TPU matrix, the traditional solution preparation method and the blade coating technique were cleverly combined to prepare the SiO2@TPU composite coating fabric. The specific preparation method is as follows:

[0064] S1. Thermoplastic polyurethane (TPU) pellets are added to a DMF solution and magnetically stirred to produce a coating precursor solution. During this process, friction between the pellets and the solvent, between the pellets, and between the pellets and the instrument wall generates heat. This, combined with external heating from the instrument, causes the TPU to quickly soften and exhibit strong adhesion properties.

[0065] S2: Nano-SiO2 particles are added to the TPU coating precursor solution and finely crushed using an ultrasonic disperser to obtain a coating finishing solution. The surface treatment agent can more effectively treat the nanoparticles locally, significantly reducing the surface energy of the particles and avoiding the re-aggregation of the hydrophobic SiO2 nanoparticles. The viscous drag force of the TPU and the high shear force generated by the ultrasound work together to ensure uniform coating between the hydrophobic SiO2 nanoparticles and the TPU pellets.

[0066] The fabric is cotton, polyester, nylon or a blended fabric, preferably polyester Oxford fabric.

[0067] The radiant cooling self-cleaning coating finishing liquid and the polyester Oxford fabric are coated with a blade coating machine using a blade coating technique to form a stable coating fabric. The specific steps are as follows:

[0068] Step 1: Fix the white polyester Oxford fabric 2 on the PET film and use a heating device to flatten the polyester Oxford fabric to ensure uniform subsequent coating preparation;

[0069] Step 2: Fix the PET film containing polyester Oxford cloth on the equipment workbench;

[0070] Step 3: Set the parameters of the scraper coating machine, set the temperature to 20℃-30℃, turn on vacuum adsorption, set the scraper speed to 20mm / s, and set the scraping length to 200mm;

[0071] Step 4: Pour the coating finishing liquid evenly on the scraper, start the scraper coating machine, and drive the coating finishing liquid to move at a constant speed until it is evenly covered on the surface of the polyester Oxford cloth;

[0072] In step 5, the coating solution is naturally cooled to room temperature to obtain a radiant cooling self-cleaning coating 1. A quality inspection is then conducted to ensure that the surface is smooth, wrinkle-free, bubble-free, and that the adhesive strength and hydrophobicity meet the standards. This results in a radiant cooling self-cleaning coated fabric. Garments made with this radiant cooling self-cleaning fabric coating offer a cooling, comfortable, and self-cleaning effect.

[0073] Comparative Example 1

[0074] A common white polyester Oxford fabric, also the base fabric, has a tight structure and limited cooling capacity.

[0075] Comparative Example 2

[0076] The difference from Example 1 is that the mass percentage of TPU in the coating finishing liquid is 10.0%-10.1%, and the mass percentage of PVDF in the coating finishing liquid is 4.3%-4.4%.

[0077] Comparative Example 3

[0078] The difference from Example 1 is that the mass percentage of TPU in the coating finishing liquid is 8.5%-8.6%, and the mass percentage of PVDF in the coating finishing liquid is 5.6%-5.7%.

[0079] Comparative Example 4

[0080] The difference from Example 1 is that the mass percentage of TPU in the coating finishing liquid is 5.6%-5.7%, and the mass percentage of PVDF in the coating finishing liquid is 8.5%-8.6%.

[0081] Comparative Example 5

[0082] The difference from Example 1 is that the mass percentage of TPU in the coating finishing liquid is 7.0%-7.2%, the mass percentage of PVDF in the coating finishing liquid is 7.0%-7.2%, and the mass percentage of hydrophobic silica in the spinning solution is 0%.

[0083] Comparative Example 6

[0084] The difference from Example 2 is that the mass percentage of hydrophobic silica in the spinning solution is 7.2%-7.3%.

[0085] The synergistic cooling functional fabrics in Examples 1-2 and Comparative Examples 1-6 were tested for radiative cooling performance and self-cleaning performance. The results are shown in Table 1. The testing conditions for radiative cooling performance, air permeability and hydrophobicity were: ambient temperature 18°C, convection heat release coefficient 10 W / m 2 *K, air mass AM1.6, atmospheric pressure 100 Pa. Radiant cooling performance is tested using an outdoor daytime cooling test, using the temperature difference as the test metric. A smaller value indicates better performance. Hydrophobicity is tested using the contact angle. A larger contact angle indicates better hydrophobicity and improved stain and dirt resistance.

[0086] Table 1 Test records

[0087]

[0088] From the results in Table 1, it can be seen that the fabric of Example 1 is made of radiative cooling self-cleaning coating fabric, which achieves a better synergistic effect of radiative cooling effect and anti-fouling performance.

[0089] Compared to Example 1, Example 2 exhibits a poorer radiative cooling effect. This is because the coating composed of a single TPU matrix system has a flat microstructure, minimal voids, and weak scattering. In contrast, in the PVDF / TPU copolymer matrix system, PVDF contains more rigid segments, while TPU contains more flexible segments. This combination makes the two polymers incompatible within the system, promoting interweaving of the molecular chains. The flexible segments provide elasticity to the mixed polymers, while the rigid segments serve as linear connection points, enhancing the mechanical properties of the coating. Furthermore, this structure creates more porous structures on the coating surface, significantly increasing its scattering ability, thereby significantly improving the cooling effect.

[0090] Compared with Example 1, the radiant cooling effect of Comparative Examples 2 and 3 is poor, which shows that the ratio of PVDF and TPU is crucial. Scanning electron microscopy observation of the coating surfaces of Comparative Examples 2 and 3 shows that when the mass percentage of PVDF is low, the coating cannot completely cover the surface fibers of the Oxford cloth, and part of the fabric surface is exposed. This will lead to uneven radiant cooling effect, thereby affecting the overall radiant cooling effect. When the mass percentage of TPU in the coating finishing liquid is 7.0%-7.2%, and the mass percentage of PVDF in the coating finishing liquid is 7.0%-7.2%, the prepared coating completely covers the surface of the Oxford cloth fabric, resulting in better radiant cooling performance and hydrophobic self-cleaning properties.

[0091] Compared with Example 1, the radiative cooling effect of Comparative Example 4 is almost the same, and the improvement in hydrophobic self-cleaning performance is not obvious. This shows that although PVDF has excellent radiative cooling performance, it has a cooling limit. When the mass percentage of TPU in the coating finishing liquid is 7.0%-7.2% and the mass percentage of PVDF in the coating finishing liquid is 7.0%-7.2%, if the PVDF content is further increased, the radiative cooling performance and self-cleaning performance will not be further improved, and the preparation cost will increase. Therefore, Example 1 has equivalent functionality and is more economical.

[0092] Compared with Example 1, the radiative cooling effect of Comparative Example 5 is poor. This shows that in Example 1, by adding SiO2 nanoparticles to the coating finishing liquid, the emissivity of the fabric in the atmospheric window band (8μm to 13μm) is effectively enhanced. The Si-O-Si bond vibration absorption peak of SiO2 nanoparticles matches this band, thereby improving the radiative cooling effect. In contrast, although Comparative Example 5 also uses PVDF and TPU, it does not add SiO2 nanoparticles, so its radiative cooling performance is inferior to that of Example 1. In addition, the addition of SiO2 may also improve the microstructure of the fabric, adding more microporous structures, and improving the scattering performance.

[0093] Compared with Example 2, the coating of Comparative Example 6 has an improved radiant cooling effect, but at the same time, a powder floating phenomenon occurs. This shows that increasing the SiO2 content does help to enhance the radiant cooling effect. However, while increasing the SiO2 filler, it also causes the SiO2 particles on the coating surface to fall off. When dimethylformamide DMF evaporates, although the TPU matrix can connect the SiO2 particles, the excess SiO2 particles may exceed the binding capacity of TPU, causing these particles to fall off from the coating surface. This phenomenon not only affects the overall performance of the coating, but may also have a negative impact on the user experience. Therefore, while improving the radiant cooling effect, it is necessary to carefully control the amount of SiO2 added to avoid the occurrence of powder floating.

[0094] The above description fully discloses the specific embodiments of the present invention. It should be noted that any modifications made by those skilled in the art to the specific embodiments of the present invention do not depart from the scope of the claims. Accordingly, the scope of the claims of the present invention is not limited solely to the foregoing specific embodiments.

Claims

1. A method for preparing a radiant cooling self-cleaning coated fabric, characterized in that: Polyvinylidene fluoride (PVDF) and thermoplastic polyurethane (TPU) were used as matrices to prepare PVDF / TPU copolymers. Nano-silica SiO2 particles were doped into the PVDF / TPU copolymers to ensure that the nano-SiO2 particles were evenly distributed in the PVDF / TPU copolymers to obtain SiO2@PVDF / TPU coating finishing liquid. The SiO2@PVDF / TPU coating finishing liquid was compounded with the fabric through a doctor blade coating machine to form a stable SiO2@PVDF / TPU coated fabric, namely, a radiant cooling self-cleaning coated fabric.

2. The method for preparing the radiant cooling self-cleaning coated fabric according to claim 1, characterized in that: The coating finishing liquid is prepared by dissolving PVDF in DMF solution, stirring and mixing at 50°C to 60°C for 1h to 2h to obtain a precursor solution, dissolving TPU in the precursor solution, stirring and mixing at 20°C to 30°C for 0.5h to 1h, and then adding nano-SiO2 particles. The coating finishing liquid is prepared by degassing with 60-100W ultrasound for 30-60 minutes, and the nano-SiO2 particles are hydrophobic silicon dioxide.

3. The method for preparing the radiant cooling self-cleaning coated fabric according to claim 2, characterized in that: The mass ratio of PVDF to TPU in the PVDF / TPU copolymer is 9-11:

10.

4. The method for preparing the radiant cooling self-cleaning coated fabric according to claim 2, characterized in that: The mass ratio of nano-SiO2 particles: PVDF / TPU copolymer is 14-15:

50.

5. The method for preparing the radiant cooling self-cleaning coated fabric according to claim 1, characterized in that: The fabric is cotton, polyester, nylon or a blended fabric.

6. The method for preparing the radiant cooling self-cleaning coated fabric according to claim 5, characterized in that: The fabric is polyester Oxford cloth.

7. The method for preparing the radiant cooling self-cleaning coated fabric according to claim 1, characterized in that: The scraper speed of the scraper coater is 20 mm / s, and the scraping length is set to 200 mm.

8. The method for preparing the radiant cooling self-cleaning coated fabric according to claim 1, characterized in that: The thickness of SiO2@PVDF / TPU coating is 500μm.

9. The method for preparing the radiant cooling self-cleaning coated fabric according to any one of claims 1 to 8, characterized in that: The specific preparation method of the SiO2@PVDF / TPU coated fabric is as follows: S1. Add polyvinylidene fluoride (PVDF) pellets to a DMF solution and magnetically stir at 50°C to 60°C for 1 to 2 hours to obtain a softened PVDF precursor solution. S2. Add thermoplastic polyurethane (TPU) pellets to the softened PVDF precursor solution and magnetically stir at 20° C. to 30° C. for 0.5 h to 1 h to obtain a PVDF / TPU copolymer precursor solution. S3, adding nano-SiO2 particles to the PVDF / TPU copolymer precursor solution, and performing ultrasonic treatment with an ultrasonic disperser at a power of 60 to 100 W for 30 to 60 minutes to achieve fine crushing of the nano-SiO2 particles and degassing of the solution to obtain a coating finishing solution; S4. The coating finishing liquid is evenly coated on the surface of the fabric by a doctor blade coating machine to obtain a radiant cooling self-cleaning coating fabric.

10. A radiative cooling self-cleaning coated fabric prepared by the preparation method according to claim 9.

Images